Three distinct septic systems designed for onsite removal of nitrogen (N) from residential wastewater were installed at the Massachusetts Alternative Septic System Test Center (MASSTC) and at homes across Suffolk County (SC), New York. All configurations featured nitrifying sand beds coupled with denitrifying biofilters composed of 1) a lined, saturated sand and woodchip layer, 2) a saturated box filled with woodchips, or 3) an unlined, unsaturated sand and woodchip layer. Total N (TN) in final effluent discharge from the three systems at MASSTC over more than two years were 7.1 ± 7.8, 4.3 ± 4.2, and 6.9 ± 8.4 mg N L⁻¹, respectively representing TN reductions of 83%, 87%, and 84% from influent TN. Systems at MASSTC also removed on average 90.0–99.9% of 10 of 11 organic contaminants in pharmaceutical and personal care products, microbes indicative of pathogens, and biochemical oxygen demand. Over periods up to 16 months from start-up, effluent from three lined, one woodchip box, and three unlined systems in SC averaged 8.3 ± 9.2, 5.3 ± 3.7, and 8.7 ± 4.9 mg-TN L⁻¹ representing removal rates of 90%, 94%, and 88%, respectively. For all systems, wastewater N was effectively nitrified year-round; N removal varied seasonally as denitrification attenuated in winter. Substantial quantities of TN were removed in the sand beds, likely due to denitrification in anoxic micro-zones. While elevated levels of carbon leached from the wood-based biofilters installed at MASSTC during the first 60 days of operation, no substantial decline in dissolved organic carbon or N removal was observed between the first 15 months of operation and the following 12 months. Collectively, the performance of these non-proprietary, passive systems suggest they may be a useful alternative septic system for protection of groundwater from elevated levels of N, organic contaminants, and pathogens.

在马萨诸塞州替代性化粪池系统测试中心（MASSTC）和纽约州萨福克郡（SC）的家庭中，安装了三种设计用于现场去除居民废水中氮（N）的独特化粪池系统。所有配置均以硝化砂床和反硝化生物滤池为特征，这些滤池由1）衬里的饱和沙子和木屑层组成； 2）装有木屑的饱和箱；或3）无衬里的不饱和沙子和木屑层组成。超过两年，MASSTC的三个系统的最终排放物中的总N（TN）为7.1±7.8、4.3±4.2和6.9±8.4 mg N L ^-1分别代表进水TN的TN减少83％，87％和84％。MASSTC的系统还平均去除了药品和个人护理产品中的11种有机污染物，指示病原体的微生物以及生化需氧量中的10种有机污染物的90.0–99.9％。在启动后长达16个月的时间内，SC中三个衬里，一个木屑盒和三个未衬里系统的废水平均为8.3±9.2、5.3±3.7和8.7±4.9 mg-TN L ^-1分别代表90％，94％和88％的去除率。对于所有系统，废水N全年都被有效地硝化。随着冬季反硝化作用减弱，氮去除量随季节变化。可能由于缺氧微区中的反硝化作用，在砂床上除去了大量的TN。在运行的前60天内，虽然从安装在MASSTC上的木质生物滤池中滤出的碳水平升高，但在运行的前15个月至随后的12个月之间，未观察到溶解的有机碳或氮去除量的大幅下降。总的来说，这些非专有的被动系统的性能表明，它们可能是有用的替代化粪池系统，用于保护地下水免受高水平的N，有机污染物和病原体的侵害。